1. Field of the Invention
The present invention relates in general to automotive meters, and more particularly to automotive meters of a type which can provide a so-called gradiation illumination to a dial board and its background. More specifically, the present invention is concerned with the automotive meters of an internal illumination type which can provide the viewers with a stereo effect impression as if the dial board were floating in the air.
2. Description of Known Technique
In order to clarify the task of the present invention, one of known automotive meters will be briefly described, which is shown in Japanese Patent First Provisional Publication 9-68442.
As is shown in FIGS. 5 and 6 of the accompanying drawings, the publication shows a combination meter of a motor vehicle, which comprises generally a speedometer 1, a tachometer 2, an engine temperature meter (viz., meter for indicating the temperature of engine cooling water) 3 and a fuel meter 4 which are all installed in a case 5. The combination meter further comprises four illumination structures each being constructed to illuminate an annular peripheral portion 7 of a circular dial board 6 of the meter 1, 2, 3 or 4.
In FIG. 6, there is shown in a sectional manner the four illumination structures. Since these structures are substantially the same, only the illumination structure for the speedometer 1 will be described for simplification of description.
As shown, behind the dial board 6, there are arranged a pointer mover 9 and a plurality of light sources 10 (such as electric lamps or the like) which are held by a lower case 8. The light sources 10 are arranged to circularly surround the pointer mover 9. Around the dial board 6, there is disposed an annular light conducting ring 11 whose rear edge is exposed to the spaces where the light sources 10 are located. A cylindrical case 12 extends forward from a peripheral portion of the circular dial 5 board 6. However, as shown, a rear end of the cylindrical case 12 is somewhat separated from the dial board 6 thereby to constitute an annular space 13 which extends circularly along the periphery of the dial board 6. As shown, a front edge of the annular light conducting ring 11 is exposed to the annular space 13. Thus, when the light sources 10 are energized, light from each light source 10 enters the light conducting ring 11 from the rear edge of the ring 11 and emits toward the annular space 13 from the front edge of the ring 11. Thus, the annular peripheral portion of the circular dial board 6 is illuminated. As shown, the cylindrical case 12 is shaped conical with a diameter which gradually increases with increase of distance from the dial board 6. With this conical shape of the cylindrical case 12, a gradiation illumination appears around the periphery of the circular dial board 6 by the light emitted thereto through the annular space 13.
However, even the above-mentioned known automotive meter has failed to provide viewers with satisfied visibility due to the following reasons. That is, the stereo effect provided by the gradiation illumination on the conical inner surface of the cylindrical case 12 is not satisfied. Furthermore, due to an inevitable structure for the light transmitting toward the dial board 6 through the annular space 13, satisfied light illumination is not achieved on the inner surface of the cylindrical case 12, which tends to make the stereo effect on the dial board 6 poor.
It is therefore an object of the present invention to provide an automotive meter which is free of the above-mentioned shortcomings.
According to a first aspect of the present invention, there is provided an automotive meter which comprises a ring-shaped light conducting body having therein a generally conical through bore whose diameter gradually reduces with increase of distance from a front end thereof toward a rear end thereof; a light conducting dial board installed in the conical through bore with its front face facing toward the front end of the ring-shaped light conducting body, the dial board having a peripheral edge separated from an inner surface of the conical through bore of the ring-shaped light conducting body thereby to define therebetween a certain clearance; a supporting plate arranged to position the light conducting dial board with respect to the ringshaped light conducting body; and a light source positioned behind the rear end of the ring-shaped light conducting body, so that light from the light source enters the ring-shaped light conducting body through the rear end of the same.
With the arrangement as defined in the first aspect, the following advantages are expected.
Since the light source is positioned behind the rear end of the ring-shaped light conducting body that has the generally conical through bore and the diameter of the through bore gradually reduces with increase of distance from the front end toward the rear end, the illumination degree of the conical inner surface gradually lowers as the distance from the light source increases, which provides the viewers with a fantasized impression. That is, the graduation illumination of the conical inner surface of the bore can provide viewers with such an impression as if the dial board 25 were floating in the air.
According to a second aspect of the present invention, there is provided an automotive meter which comprises a light conducting body having front and rear ends and having a generally conical through bore defined therein, whose diameter gradually reduces with increase of distance from the front end toward the rear end, the conical through bore including a front bore part defined by a sloped surface and a rear bore part defined by a concave surface; a light conducting dial board installed in the conical through bore with its front face facing forward and positioned in the vicinity of the junction portion between the front and rear bore parts, the dial board having a peripheral edge separated from the inner wall surface of the conical through bore thereby to define therebetween a circumferentially extending given space; a light conducting supporting plate attached to a rear surface of the dial board, the supporting plate being formed with a light transmitting portion which extends rearward and has an rear end intimately received in a recess formed in the rear end of the light conducting body; a plurality of light sources positioned behind the rear end of the light conducting body; a first light introducing structure defined by the rear end of the light conducting body, from which light from the light sources enters the light conducting body and travels toward the sloped and concave surfaces of the front and rear bore parts to illuminate the same from within; and a second light introducing structure defined by the light conducting supporting plate, through which light from the light sources enters the light conducting supporting plate and travels toward the dial board to illuminate the same from within.
According to a third aspect of the present invention, there is provided an automotive meter which comprises an annular light conducting body having front and rear ends and having a generally conical through bore defined therein, whose diameter gradually reduces with increase of distance from the front end toward the rear end, the conical through bore including a front bore part defined by a sloped surface and a rear bore part defined by a concave surface; a circular light conducting dial board installed in the conical through bore with its front face facing forward and positioned in the vicinity of the junction portion between the front and rear bore parts, the circular dial board having a peripheral edge separated from the inner wall surface of the conical through bore thereby to define therebetween an annular space; a circular light conducting supporting plate attached to a rear surface of the circular dial board, the circular supporting plate being formed with a cylindrical wall portion which extends rearward and has an annular rear end intimately received in an annular recess formed in the rear end of the light conducting body; a plurality of light sources circularly arranged behind the rear end of the light conducting body; a flat surface defined by the rear end of the light conducting body, the flat surface facing the light sources; and inclined portions integral with the circular light conducting supporting plate, the inclined portions having leading ends directed toward the light sources respectively.